Rectifiers, i.e. devices which convert an electrical voltage of one level to an electrical voltage of another level are well known in the art, and usually involve a transformer, and a set of components on either side of the transformer, the two sides commonly being known as the primary (input) and secondary (output) side. Rectifiers which convert a first DC-voltage level to a second DC-voltage level are also well known, and usually involve a set of switches on the primary and secondary sides, in order to make it possible to use a transformer with DC-voltages. In conventional such devices, a pair of switches on the primary side is linked to a pair of switches on the secondary side, so that the linked pairs of switches on either side of the transformer are turned on and off simultaneously, often with the same control signal or control voltage.
A well known problem in DC/DC-rectifiers is the efficiency of the device, and thus also the losses, the desire naturally being for as high an efficiency as possible, and as low losses as possible.
In DC/DC-rectifiers, there is a phenomenon known as “freewheeling”, which occurs during periods when the switches on the primary side are turned off, and the current on the secondary side circulates “freely” on the device's secondary side trough the load R.
One source of losses, and thus of heat development in the device, comes form the fact that current passes through the transformer on the secondary during the freewheeling period. Another source of losses is switching losses in the primary and secondary side switches.